The Pennsylvania Supreme Court invalidated the existing map last month as an unconstitutional gerrymander, ruling that Republican lawmakers had marginalized Democratic voters in an effort to win more seats in the U.S. House of Representatives. A new map is expected to boost Democrats' chances of winning more seats in November's midterm elections and in turn increase their odds of winning back the House from Republican control.

"The analysis by my team shows that, like the 2011 map, the map submitted to my office by Republican leaders is still a gerrymander," Wolf said in a statement. "Their map clearly seeks to benefit one political party, which is the essence of why the court found the current map to be unconstitutional."

The court's Democratic majority had given Wolf until Thursday to decide whether to accept or reject the new map submitted by Republican leaders late on Friday. With no deal in place, the court has said it will undertake the process of drawing new lines itself, with help from an independent redistricting expert.

Legal battles are playing out in several U.S. states over partisan gerrymandering, the process by which district lines are manipulated to favor one party over another. Pennsylvania has long been seen as one of the worst offenders, with one of its more oddly shaped districts described derisively as "Goofy Kicking Donald Duck."

Republicans have held 13 of the state's 18 congressional seats since the current map took effect ahead of the 2012 elections, despite Pennsylvania's status as a closely contested swing state.